Overload device



- A. R. SANBORN. OVERLOADIDEVICE.

"APPLICATION FILED acme. 91s.

1 ,328/157. Patented Jan. 20, 1920.

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fITtbuT R, Sanborn, b9 a His flt tomegf UNITED STATES PATENT oFFIc-E.

ARTHUR B. SANBORN, 0F SOi-IENECTADY, NEW YORK, ASSIGNOR 'IGGENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK. I

OVERLOAD nnvicn.

Specification of Letters Patent. Patented Jan. 20, 1920.

Application filed October 26, 1916. Serial No. 127,806.

To all whom it may concern. I

Be it known that I, ARTHUR R. SANBoRn, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Overload Devices, of which the following is a specification.

My invention relates. to devices for controlling electric circuits and has for its obj ect the provision of'improved means whereby an electric circuit may be opened and closed in a reliable, safe and eflicient manner.

More specifically, my invention relates to an improveddevice for closing 'and opening an electric circuit at the will of the operator, and so arranged as to automatically open the circuit upon the occurrence of an overload and to prevent the alternate closing and opening of the circuit until the overload has been removed.

Referring tothe drawings which show one embodiment of my invention, Figure 1 shows the structural features of my improved overload device, and Fig. 2 shows the application of my inventionof the control of an electric motor; the circuit connections, the overload device and other apparatus being shown diagrammatically for the sake of clearness.

Referring first to Fig. 2, the.circuit to be protected and controlled includes the electric motor M having an armature and series field which receive energy from the supply conductors 1 and 2 upon the closing of a circuit including the contactors having the electromagnetically-actuated contacts 3 and 4. The actuating windings 5 and 6, respectively, of these contactors are energized through a circuit including the normally closed overload switch 7 and the pilot or manually operated switch 8. The series coil 9 included in the motor circuit is adapted to raise an armature 0r plunger 10 in response to an overload in the motor circuit, mechanically raising the overload switch 7 and cause this. switch to make electrical contact with the' core 11 of a normally deenergized retaining magnet. The coil ofthis magnet has one of its termmals electrlcally connected to the core 11 and the other terminal connected through a resistance to the supply conductor 1. When the overload switch 7 is moved into contact with the core 11 upon the occurrence of an overload in the motorcircuit, the circuit of windings 5 and 6 is opened, the contacts 3 and 1 are opened and the retaining magnet is energized through a local circuit including the overload switch 7 and the manually operated switch 8. Due to the energization of the coil 12, the overload switch I is retained in the upper position until the manually operated switch 8 is opened. When the switch 8 is opened, the coil 12 is deenergized, the overload switch 7 is permitted to drop and the circuit of the windings 5 and 6 is energ ized when the switch 8- is again closed. he pilot switch 8 may be located at any convenient place, and this is usually at a remote point from the motor, the contactors and the overload device.

Referring now to Fig. 1, showing the structural features of the preferred form of my overload device, the series overload winding 9 is supported in any suitable manner in the casing 13 secured to the base 14. The armature or plunger 10 of the overload device is supported in the coil .9 by means of an arm 15 secured to the casing 13 by means of the bolt 16 A slot in one end of this arm permits an adjustment of the arm and the position of the plunger withinthe coil so .as to adjust the device toopen the motor circuit at any value of current desired. The plunger 10 is adapted to cooperate with a stationary core 17 secured to' the casing 13 by means'of the nut 18. The overload switch 7 is adapmd to be mechanically raised by anonmagnetic extension 19 on the plunger which moves up and down through a hole in the core 17 The retaining magnet 20 has one terminal of its coil 12 electrically connected to the core 11 and the support 21, and the armature 22 for the retaining magnet is secured to the overload switch 7, the arrangement being such that by means of a spring or other suitable means.

The operation of my invention is as fol-.

lows:

Closing the manually operated switch 8 energizes the windings 5 and 6 of the con,

tactors, the circuit being from the supply v supply conductor 2.

The series contactor 26 is of the well known type which is held open when the current through its operating coil is hi h and is automatically magnetically close when the current drops to a predetermined value. WVhen, therefore, the armature. current drops to the desired predetermined value, theseries contactor 26 will close and short circuit the starting resistance R.' If at any time the motor circuit is deenergized, as, for instance, upon the occurrence of an overload,the series contactor 26 will open and reinsert the starting resistance R in the armature circuit preparatory to again starting the motor.

It will be noticed that my arrangement requires but one conductor between the manually operated switch 8 and the line contactors, and this is an advantage where re mote control is necessary and it is very desirable to limit the number of conductors, as, for instance, on shipboard. With the start-- ing resistance cut out and the motor running at its normal speed, if an overload occurs in the motor circuit, the overload coil 9 will cause the plunger 10 to be raised and the end of the extension 19 will engage the over-. load switch 7, mechanically'lifting the overload switch out of engagement with the electrode 23 included in the circuit of the windings 5 and 6 of the contactors, causing these-contactors, as'well as the series con- .tactor 26, to open and the plunger 10 to drop. The end of the overload switch will "almost immediately thereafter be brought .into engagement with the electrode 24 and the coil 12 of,the normally deenergized retaining magnet will be energized through a local circuit including the manually operated switch 8, the overload switch 7, core 11 of the retaining magnet, coil 12 of this magnet, through the limiting resistance to the supply conductor 1. magnet thus energized, the armature 22 on the overload switch will be attracted by the core -11 and the overload switch held in its raised position until the switch 8 is opened. When, therefore, the motor is stopped by the occurrence of an overload it will not With the retaining start again until the attendant returns and" opens and recloses the switch 8. The vibration of the overload switch 7 between open and closed position .tvhich would otherwise occur due to the ntlnued presence of the overload and wlnch would be a source of danger is thus avoided.

For the protection of circuits where overloads occur, infrequently, it is particularly desirable that the retaining magnet for the overload switch be normally deenergized in order to avoid any waste of current, and

that when an overload does occur the control switches. will be positively opened and malntained opened until the overload ceases. My arrangement is particularly advantageous in these respects, since the retaining' i that the invention can be carried out by other means.

\Vhat I clann as new and desire to secure by Letters Patent of the United States, is,

1. The combination with a circuit controlling electromagnetically actuated contactor, of means for opening the contactor and maintaining it open upon the occurrence of an overload, comprising a mechanically opened overload switch magnetically held in its open position by a normally dee'nergized magnet whicli'is energized when the overload occurs through a circuit including the overload switch;

2. The combination with an electric motor of a contactor for controlling the starting thereof, an overload switch for denergizing the contactor to stop the motor upon magnet energizedonly when the overload switch is in its operated position and a'rranged to hold the overload switch open, and a manually operated switch controlling the circuit of the retaining magnet and of the contactor through the overload switch.

3. The combination with an electric motor of a contactor for controlling the starting thereof, an overload switch for deenergizing the contactor to stop the motor upon the'occurrence of an overload, a retaining magnet energized only when the overload switch is in its operated position and arranged to hold the switch open, and a manually operated switch for closing the circuit of the retaining magnet through the overthe occurrence of a'n-overload, a retaining switch for maintaining the ma load switch in its operated position, and for closing the circuit of the contactor through the .overload switch in its normal position.

et. The combination with a contactor having a winding adapted to close the same, of a circuit for the winding having therein a normally closed overload switch, a normally denergized retaining coil for the overloadswitch, means responsive to an overload for moving the overload switch to open the cir- V cuit of the contactor winding and energize the retaining coil through a circuit including the overload switch to prevent the overload switch resuming its normal position after the contactor is opened.

5. The combination with a contactor having a winding adapted to close the same, of a circuit for the winding having therein a normally closed overload switch, a normally denerglzed retaining coil for the overload switch, means responsive to an overload for moving the overload switch to open the circuit of the contactor windin and close the circuit of the retaining coi through a circuit including the overload switch to prevent the overload switch resuming. its normal position after the contactor is opened, and manually operated means in series with the overload switch for controlling the conand a normally deenergized magnet energized, upon the occurrence of an overload, through a local circuit including the over-' load switch and the manually operated et circuit of the contactor open until t e manual switch is operated.

7'. The combination with a contactor having a winding adapted to close the same, of. a circuit for the winding having therein an overload switch biased to the closed posioverload switch closing the circuit of the contactor winding while the retaining magnet is energized.

8. The combination with a contactor having a winding adapted to close the same, of

a circuit for the winding having therein an overload switch biased to the closed position, a normally denerglzed retalning magergized, and'manually operated means for controlling the circuits of the contactor winding and the "retaining magnet.

9. The combination with a contactor having a winding adapted to close the same, of a circuit for said winding having therein an overload switch normally biased to the closed position, a normally denergized retaining magnet for the overload switch, the said retaining magnet having one terminal of its coil connected to its magnet core and the other terminal connected to a supply con ductor, means responsive to an overload for moving the overload switch against its bias into electrical contact with the core of the retaining magnet thus denergizing the winding circuit of the contactor and energizing the coil of the retaining magnet through the overload switch to prevent the overload switch resuming its normal position after cessation of the overload.

10. The combination with acontactor having a winding adapted to close the same, of a circuit for the winding having therein an overload switch normally biased to the closed position, ,a retaining magnet having one terminal of its coil connected to its magnet core and the'lother terminal connected to a supply conductor, an armature for the retaining magnet onthe overload switch, a relay having an overload coil and an adjustable means for moving the overload switch against its biasinto electrical contact with the core of the v retaining'magnet, upon the occurrence of air overload, thus denergizing the windingcircuit of the contactor and energizing the c' il of the retaining magnet to attract its armature and prevent the overload switch res'uming its normal position after cessation the overload, and a man ually operated switch, for controlling the contactor and the retaining magnet.

11. The combination with an electric motor of a contactor for controlling the starting thereof and means for opening the contactor and maintaining it open upon the occurrence of an overload comprising an overload switch for o ening the circuit of the contactor upon the occurrence of an overload, an electro-magnet havin a winding connected to a circuit which is independent of the contactor winding and arranged to be energized by the opening of the over.- load switch and a manually operated switch in series with the overload switch in the open position of the overload switch and controlling the circuit of the contactor Windingin the closed position of the overload switch.

' 12. The combination with a circuit controlling electromagnetlcally actuated contactor, of a normally closed overload switch for controlling the energization of said contactor, a normally denergized retaining niagnet for maintaining the overload switch in the open position upon the occurrence of an overload, a pilot switch for controlling the contactor and the retainingmagnet, and connections whereby closing the pilot switch energizes the contactor winding through a circuit including the overload switch, and upon the occurrence of an overload the contactor is deenergized and the retaining magnet is energized to hold. the overload switch open through a circuit including the pilot switch and the overload switch.

In witness whereof, I have hereuntov set my hand this 25th day of October, 1916.

ARTHUR B. SANBOBNr 

